Emergency cooling apparatus for a production well



INVENTORS H. w. PARKER R. F. MELDAU W" ATTORNEYS H.W. PARKER E AL Original Filed Dec. 13, 1965 EMERGENCY COOLING APPARATUS FOR A PRODUCTION WELL July 29, 1969 COM PRESSED GAS PRODUCTION United States Patent "ice U.S. Cl. 166-53 5 Claims ABSTRACT OF THE DISCLOSURE In controlling downhole temperature in an in situ combustion production well to prevent damage to the downhole equipment, water is injected at a controlled rate through a water conduit extending to the downhole area in response to sensed pressure or temperature downhole. When a sudden temperature and pressure condition occurs downhole in a deepwell and the demand for water is suddenly greatly increased, the pressure downhole prevents flow of water into the downhole area for a substantial period and damage to the casing and production tubing is apt to occur. To assure almost immediate delivery of the required water under emergency conditions of this nature, high pressure gas is injected into the upper end of the water conduit at sufficient pressure to overcome the downhole pressure and force water out of the lower end of the water-conduit.

This is a divisional application of copending application Ser. No. 513,469, filed Dec. 13, 1965, now US. Patent No. 3,382,923.

This invention relates to a process and arrangement of apparatus for controlling cooling-water injection into a hot production well downhole during emergency conditions.

Copending application Ser. No. 43 0,000 of R. F. Meldau et al., filed Feb. 3, 1965, now Patent No. 3,343,598, discloses and claims a process and arrangement of apparatus for controlling the injection of cooling water downhole in a well adjacent a hot stratum during in situ combustion operation. The invention in said application is effective under all normal operating conditions to control the downhole temperature so as to avoid overheating the wellbore and downhole equipment. However, under emergency conditions wherein the wellbore temperature and pressure rapidly rise for any reason, such as wellbore ignition downhole in the production well, there may be a period of 5 minutes or more during which water does not enter the wellbore downhole from the water injection conduit. When this happens, the temperature rises sufficiently to damage or destory downhole equipment for effective use in the production process.

When producing from a stratum such as one about 2000' below surface level, the water level in the water injection conduit is well below the wellhead because the pressure in the upper end of this conduit is substantially below atmospheric. This causes no problem in normal operation; however, with wellbore ignitions occurring accompanied by pressure surges, increased pressure reduces water flow into the injection conduit or shuts off water flow entirely until the water level in the tubing rises sufiiciently to balance the new, higher pressure. Since this may take 5 minutes or more to transpire, the hot exhaust gases are certain to damage the casing and tubing in the well.

This invention is concerned with an apparatus for avoiding the problem described above and preventing damage to downhole equipment during emergency conditions downhole when the temperature tends to rise unduly from normal operating temperatures.

3,457,993 Patented July 29, 1969 Accordingly, it is an object of the invention to provide an apparatus for maintaining the flow of water into a hot production wellbore downhole during temperature and pressure surges which tend to disrupt the normal flow of water into the well downhole from a water injection conduit. A further object is to provide an improvement in the apparatus of said application Ser. No. 430,000. Another object is to provide an arrangement of apparatus for compensating for pressure and temperature surges during Water injection into a hot production well through a water injection conduit and restoring normal gas pressure in the water injection conduit after temperature and pressure conditions downhole have returned to normal. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention, as applied to the injec tion of water through a water conduit extending downhole in a production well in an oil stratum under production by in situ combustion with hot gases being produced through said Well, flow of injected water being controlled in response to sensed temperature or pressure downhole, wherein temperature and pressure suddenly rise to establish emergency conditions which tend to damage well equipment, comprises injecting high pressure gas into the upper end of the water conduit to force Water into the downhole area of the well against the higher downhole pressure during emergency conditions to reestablish normal conditions downhole. High pressure gas in the water conduit is bled off the upper end thereof as normal conditions are established.

In accordance with the invention, a gas injection conduit or line, connecting with a source of high pressure gas is tapped or otherwise connected into the upper end of the water injection conduit and provided with a normally closed valve. A device downhole for sensing either the temperature or the pressure at this locus and connected with a controller at ground level is provided. This controller is sensitive to the signal emitted by the downhole device and is in control of the valve in the gas injection line so that when above normal temperature or pressure downhole occurs, the controller opens the valve in the high pressure gas line which allows high pressure gas to invade the upper end of the water injection conduit and apply this high pressure to the column of water to overcome excessive downhole pressure and force cooling water into the wellbore adjacent the hot stratum to protect the casing and tubing in the hot area of the well.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing which is an elevation in partial section of equipment in and associated with a production well for effecting the invention.

Referring to the drawing, an oil said or other combustible carbonaceous stratum 10 is penetrated by a well 12 which is provided with a casing 14, a tubing string 16 and a water injection conduit 18 having a trap 20 and leading into the lower end of the production tubing 16. The related structure of the water injection conduit 18, tubing string 16, and trap 20 is preferably that shown in the above-identified compending application.

Numeral 22 designates either a pressure sensor or a temperature sensor, such as a thermocouple, positioned downhole adjacent stratum 10, preferably, at the most sensitive temperature and pressure control spot. This device 22 is connected by a lead line 24 to a controller 26 which is either a temperature recorded controller or a similar pressure controller. Controller 26 is connected by lead line 28 with an open coil solenoid valve 30 through a time delay switch 32. Valve 30 is positioned in high pressure gas line 34 which is connected with a source of high pressure gas such as air, nitrogen, flue gas, C0 etc. A

pressure regulator 36 may be positioned in line 34 upstream of valve 30. A cooling water supply line 38 containing a motor valve 40 connects with the upper end of water injection conduit 18 and with a suitable source of cooling water. Motor valve 40 is controlled by controller 26 operatingthrough valve 42 in instrument air line 44 so as to control the introduction of cooling water, under normal operating conditions in well 12 downhole, in order to maintain a predetermined normal temperature and/or pressure downhole.

When emergency conditions occur downhole such as ignition of the carbonaceous material in the sand around the wellbore or of produced hydrocarbon vapors, utilizing bypassed O occurring in the production well, the pressure builds up so as to prevent the influx of water from conduit 18. Under emergency conditions with a rapid rise in temperature and pressure, the introduction of water at a faster rate through valve 40 is not sutficient to take care of the emergency condition because it takes too long to build up the column of water in conduit 18 against the pressure therein to provide immediate relief for the elevated temperature condition downhole. In this case, device 22 senses the surge in temperature or pressure and transmits a proportional signal to controller 26 which actuates valve 30 through time delay switch 32 to allow high pressure gas to invade the upper end of the water injection conduit, thereby providing a slug of high pressure gas which supplies the necessary pressure to force Water out the lower end of conduit 18 into the wellbore until normal temperature and pressure conditions are restored. During this time in which high pressure gas is in the upper end of conduit 18, normally closed bleed valve 46 in vent line 48 gradually restores normal gas pressure, this valve being selected and constructed to operate above a selected normal pressure.

Time delay switch 32 is positioned in the circuit from the controller 26 to motor valve 30 so as to prevent operation of this valve in introduction of pressurizing gas during minor fluctuations in pressure or temperature sensed by device 22. This switch is designed to operate after a delay of a short period from several seconds to 30 seconds or more.

Alarm 50 is connected with controller 26 which operates the alarm when excessive pressure or temperature occurs downhole as sensed by device 22.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. In combination, well-cooling apparatus comprising:

(1) a tubing string terminating in said well downhole adjacent a carbonaceous stratum, said tubing string providing means for conducting fluids to the surface;

(2) a water conduit extending from the upper end to the lower end of said tubing string and connected with a water-supply line, said lower end of said conduit adapted to discharge cooling water for maintaining subsurface temperature;

(3) a gas supply line connected with the upper end of said water conduit and adapted to connect with a high-pressure gas supply;

(4) normally closed valve means in said gas-supply line for controlling flow of gas into said water conduit;

(5) means downhole for sensing one of pressure and and temperature conditions adjacent said stratum and sending out a signal representative of the sensed condition; and

(6) control means above ground level connected in circuit with the means of (5) and with the valve means of (4) for receiving said signal and opening said valve means when said signal indicates said pressure or temperature is above a predetermined normal value whereby pressurized gas enters the water line causing the cooling water to be discharged through said lower end at a faster rate.

2. The combination of apparatus of claim 1 wherein the means of (5) is a temperature sensor and the control means of (6) is a temperature controller.

3. The combination of apparatus of claim 1 wherein the means of (5) is a pressure sensor and the control means of (6) is a pressure controller.

4. The combination of apparatus of claim 1 including a normally closed bleed valve in a vent line connected with the upper end of the water conduit of (2) adapted to slowly vent gas therefrom at above normal pressures.

5. The combination of claim 1 wherein said control means includes an electric circuit having a time delay switch for preventing operation of said valve means upon minor fluctuations in the signal from the means of (5).

References Cited UNITED STATES PATENTS 2,347,769 5/1944 Crites 166-53 2,848,710 8/1958 Owen 166-66 X 2,973,812 3/1961 MacSporran 166-11 3,136,359 6/1964 Graham 166-11 X 3,202,219 8/1965 Parker 166-64X 3,227,215 1/1966 Marx 166-53 3,343,598 9/1967 Meldau et a1. 166-11 3,357,490 12/1967 Holmes 166-53 CHARLES E. OCONNELL, Primary Examiner I. A. CALVERT, Assistant Examiner US. Cl. X.R. 166-64 

